如何使用 try-catch 块解决无穷大错误？

Question

我正在尝试调试我的程序，它可以捕获整数值之外的所有错误并使用 try-catch 进行报告。当我输入一个字符串时，我得到了无限环回，不知道如何停止它。

import java.util.Scanner;
import java.lang.ArithmeticException;
import java.util.InputMismatchException;

public class Divide {
    public static void main(String[] args) {

        int num1 = 0;
        int num2 = 0;
        double ratio;
        Scanner scan = new Scanner(System.in);
        int x = 1; // using variable for do-while loop

        do { // re-runs code if input error
            try {
                System.out.println("Let's divide some numbers!");
                System.out.print("Enter your first number: ");
                num1 = scan.nextInt();
                System.out.print("Enter your second number: ");
                num2 = scan.nextInt();
                ratio = ((double) num1 / num2);
                System.out.println("Eureka!  the answer is " + ratio);
                x = 2;
            } catch (ArithmeticException e) {
                System.out.println("No division by zero!");
            } catch (Exception e) {
                System.out.println("This won't work. Try again.");
            }

        } while (x == 1);
    }
}

输出： 让我们划分一些数字！ 输入您的第一个整数：Y 输入错误：null让我们除以一些数字！ 输入您的第一个整数： 输入错误：null 让我们除以一些数字！ 输入您的第一个整数：输入错误：null让我们除以一些数字！

Answer 1

你需要类似的东西吗：

import java.util.Scanner;

public class Divide {
    public static void main(String[] args) {

        int num1 = 0;
        int num2 = 0;
        double ratio;
        Scanner scan = new Scanner(System.in);
        int x = 1; // using variable for do-while loop

        do { // re-runs code if input error
            try {
                System.out.println("Let's divide some numbers!");
                System.out.print("Enter your first number: ");
                num1 = scan.nextInt();
                System.out.print("Enter your second number: ");
                num2 = scan.nextInt();
                if (num2 != 0) {
                    ratio = ((double) num1 / num2);
                    System.out.println("Eureka!  the answer is " + ratio);
                } else {
                    System.out.println("The second number should not be 0");
                }
            } catch (Exception e) {
                System.out.println("This won't work. Try again.");
                x = 2;
            }
        } while (x == 1);
    }
}

示例运行：

Let's divide some numbers!
Enter your first number: 10
Enter your second number: 5
Eureka!  the answer is 2.0
Let's divide some numbers!
Enter your first number: 12
Enter your second number: 0
The second number should not be 0
Let's divide some numbers!
Enter your first number: 23
Enter your second number: 5
Eureka!  the answer is 4.6
Let's divide some numbers!
Enter your first number: 50
Enter your second number: abc
This won't work. Try again.

此时程序将停止执行。

更新：我刚刚看到您的评论，即使输入非法（例如 abc），您也不希望您的程序停止。为此，您需要做的就是再次实例化Scanner 对象。下面给出的是完整的示例运行程序：

import java.util.Scanner;

public class Divide {
    public static void main(String[] args) {

        int num1 = 0;
        int num2 = 0;
        double ratio;
        Scanner scan = new Scanner(System.in);
        int x = 1; // using variable for do-while loop

        do { // re-runs code if input error
            try {
                System.out.println("Let's divide some numbers!");
                System.out.print("Enter your first number: ");
                num1 = scan.nextInt();
                System.out.print("Enter your second number: ");
                num2 = scan.nextInt();
                if (num2 != 0) {
                    ratio = ((double) num1 / num2);
                    System.out.println("Eureka!  the answer is " + ratio);
                } else {
                    System.out.println("The second number should not be 0");
                }
            } catch (Exception e) {
                System.out.println("This won't work. Try again.");
                scan = new Scanner(System.in);
            }
        } while (x == 1);
    }
}

示例运行：

Let's divide some numbers!
Enter your first number: 10
Enter your second number: 5
Eureka!  the answer is 2.0
Let's divide some numbers!
Enter your first number: 10
Enter your second number: 0
The second number should not be 0
Let's divide some numbers!
Enter your first number: 10
Enter your second number: abc
This won't work. Try again.
Let's divide some numbers!
Enter your first number: 10
Enter your second number: 5
Eureka!  the answer is 2.0
Let's divide some numbers!
Enter your first number: 

我希望，这可以满足您的要求。如果您还需要其他东西，请随时告诉我。

现在，您甚至可以删除冗余变量x，如下所示：

import java.util.Scanner;

public class Divide {
    public static void main(String[] args) {

        int num1 = 0;
        int num2 = 0;
        double ratio;
        Scanner scan = new Scanner(System.in);

        while (true) { 
            try {
                System.out.println("Let's divide some numbers!");
                System.out.print("Enter your first number: ");
                num1 = scan.nextInt();
                System.out.print("Enter your second number: ");
                num2 = scan.nextInt();
                if (num2 != 0) {
                    ratio = ((double) num1 / num2);
                    System.out.println("Eureka!  the answer is " + ratio);
                } else {
                    System.out.println("The second number should not be 0");
                }
            } catch (Exception e) {
                System.out.println("This won't work. Try again.");
                // re-runs code if input error
                scan = new Scanner(System.in);
            }
        }
    }
}